The SZ signal thus depends on three quantities: the density of ICM electrons \(n_e\)  along the line of sight \(l\) , the ICM temperature \(T_e\) , and the bulk velocity of the ICM electrons along the line of sight \(v_z\) . The relativistic corrections inducing variations of the shape of the tSZ and kSZ spectra \(f(\nu ,T_e)\)  and \(g(\nu ,T_e,v_z)\)  are often referred to as the rSZ effect and depend directly on the value of the ICM temperature. Sampling the total SZ spectrum with at least three independent data points on a large enough frequency range thus enables estimating the ICM temperature independently from any X-ray observation. The detection of the rSZ effect has already been made using millimeter spectroscopy with Z-Spec [1]} and by stacking analyses [2]}. These studies enable measuring the mean ICM temperature of galaxy clusters but they were unable to provide resolved detection of the rSZ effect which is a prerequisite to the production of ICM temperature maps.
<FIGURE>